A rheostatic positional transducer protected for use with automotive engines is described in U.S. Patent specification No. 4,430,634. Such a rheostatic device is used, e.g., in an electronic carburetor of a motor vehicle. An article in the German publication Krafthand, No. 15, Aug. 6, 1983, pp. 877-881 describes generally such a use. The fuel-air ratio of the mixture is electronically controlled during start, cruising and acceleration. The fuel-air ratio is influenced by means of a start flap. A second servo component controls the throttle valve. A throttle-valve potentiometer, which is connected with the throttle-valve shaft by a coupling, is used to indicate the position and the movement of the throttle valve.
It is important to protect the resistor layer and the sliding spring contact in such potentiometers from external environmental conditions such as oil, dust, gasoline, exhaust gases, etc.